This invention relates to a lubricating device for automatically delivering lubricant, such as grease or oil, over an extended period of time, the lubricating device being of the kind comprising cylinder means having front wall means with a discharge outlet, rear wall means and cylindrical side walls, piston means movable within the cylinder means from a rear position to a forward position, the piston means and the side and front wall means of the cylinder means defining a variable volume chamber for containing the lubricant to be dispensed, helical spring means movable from a compressed condition to an expanded condition to release spring force for moving the piston means from its rear position towards its front position to reduce the volume of the said variable volume chamber over a period of time for expelling lubricant through the discharge outlet, and control means for controlling the movement of said spring means from its compressed condition to its expanded position and comprising an escapement mechanism, electrical means controlling the operation of the escapement mechanism and gearing connected between said escapement mechanism and said piston means
Dispensing devices for lubricants of the kind generally known as self-contained automatic lubricators were introduced almost 40 years ago and have now become widely used for dispensing lubricants into lubricant channels of machine bearings over prolonged periods of time, for example from between 1 and 12 month. Such self-contained devices are supplied to users ready-filled with lubricant for fitting temporarily to the bearings they are intended to lubricate. They are designed to lubricate for a predetermined period without further attention on the part of the user. Once that period is over and the lubricant contents have been spent, the entire lubricator is removed and replaced with another. Self-contained automatic lubricators are particularly advantageous for the lubrication of scattered and isolated bearings, such as exist, for example, in water treatment works, dockyards, traffic barriers and countless other applications. Millions of self-contained automatic lubricators are now used annually world-wide and they are steadily replacing older methods of lubricating bearings involving labour intensive replenishment of lubricant by the frequent application of hand-operated grease guns. As self-contained automatic lubricators are normally screwed directly into grease nipple sockets and are frequently required to be fitted in confined spaces, they are designed to be very compact and as light in weight as possible. The great majority of such lubricators are designed to dispense between 100 ml and 120 ml of lubricant. They typically exert pressures of about 0.5 bar or more when injecting lubricant into bearings offering no resistance to flow but are capable of exerting pressures up to 5 bar when necessary to overcome resistance to flow in the bearing. Typically, this requires the lubricators to apply forces varying from 100 N up to 1000 N in order to move pistons in lubricant chambers of from 50 to 60 mm in diameter.
Self-contained automatic lubricators of this type are relatively inexpensive and are quite different from more complicated centralised lubrication systems such as are designed for lubricating all the bearings of, for example, a single large machine inside a factory building, which are designed to be permanent fixtures, which require high operating pressures and which are bulky, heavy and expensive.
Self-contained automatic lubricators are not to be confused with some earlier types of single-point lubricator that were designed to be fixed permanently to a single bearing for refilling in-situ and which were much heavier, bulkier and more expensive. A known lubricating device of the kind referred to is described in U.S. Pat. No. 1,929,774. This device is an early type of xe2x80x9cpermanentxe2x80x9d lubricator designed to be repeatedly filled in situxe2x80x94i.e. it is not a so-called self-contained automatic lubricator of the type described above. It is supplied with electricity from an external supply and, consequently, is not self-contained. It is also relatively bulky and heavy with the escapement mechanism and associated gearing being positioned axially behind the helical spring means resulting in the lubricating device being relatively long in the axial direction.
Other known single-point lubricators that antedate self-contained automatic lubricators as described hereinbefore have spring means consisting of helical compression springs but are designed to be permanent fixtures and, unlike self-contained automatic lubricators, require frequent replenishment by means of hand-operated grease guns. On actuation of the lubricator, the energy from the spring is released to urge the piston device to move towards its forward position thereby expelling the lubricant. The helical compression spring is thus the only force generating means acting on the piston to expel the lubricant. Although the rate at which the lubricant is discharged can be influenced by substituting springs with different characteristics, by valving or by varying the discharge orifice, the actual rate of discharge of such a device on a particular bearing is governed primarily by the resistance in the bearing channels, the fluidity of the lubricant, and the ambient temperature (which affects the fluidity of the lubricant). Although such a known lubricator can be made relatively inexpensively, it does not have the facility to preset or predetermine a rate of lubricant discharge that is independent of the variable factors mentioned above. Furthermore for certain applications and operating conditions the lubricator will dispense all its lubricant within a few weeks of initiating the lubricant dispensing process.
In order to overcome the disadvantages of the known single-point lubricators, self-contained automatic lubricators have been designed in which the spring means have been replaced by actuating means which can be controlled to vary the rate of lubricant discharge in a controlled manner. In such self-contained automatic lubricators, the piston device separates the cylinder into a variable volume first chamber containing the lubricant to be dispensed and a second chamber. The second chamber contains an electrolyte into which a galvanic element comprising different metallic materials that are connected together electrically to form electrodes can be introduced from a third chamber. The resultant electro-chemical reaction gradually generates gas which moves the piston device to discharge the lubricant content. Lubricators of this type can be set to discharge over periods as long as 12 months at rates that can be predicted with limited accuracy. They have the disadvantage that the electrochemical reaction is very sensitive to changes in ambient temperature and it is necessary for users to consult tables to determine the approximate discharge rate and operating duration at specific ambient temperatures (which in working conditions can vary from as low as xe2x88x9220xc2x0 C. to as high as +55xc2x0 C.). Examples of such lubricators are described in GB-A-1,401,535 and U.S. Pat. No. 3,430,731.
Another known self-contained automatic lubricator is described in EP-A-0278138 and has a chamber containing an electrolyte together with electric batteries which enable an electric current to be passed through the electrolyte to generate gas, together with electric or electronic control means for switching on or off and/or varying the current flow and hence the rate of gas generation and the rate of discharge of lubricant. The discharge rates of such lubricators can be predicted with limited accuracy and they can operate for long durations, but they have the disadvantages that they require a relatively large battery pack to maintain the electrochemical reaction over long periods, the electrochemical reactions are temperature sensitive and the lubricators are relatively expensive.
It is also known from German G9214096.3 for a self-contained automatic lubricator to be provided with batteries and a geared down motor for driving a screw which moves the piston device to discharge the lubricant. Electric or electronic controls are provided for switching on or off and/or varying the current flow to vary the rate of discharge of the lubricant. Such known lubricators enable accurate discharge rates to be set, the rates are relatively independent of ambient temperature variations, and they can operate for long periods. However they have the disadvantages that the powerful electric motor and gearing make the lubricators heavy and bulky, they need a large battery pack to provide adequate power to operate the motor and gearing, and they are relatively expensive.
In EP-A-0598678 there is described a self-contained automatic lubricator equipped with a piston, a rotatable threaded rod, an escapement comprising a toothed wheel connected to the threaded rod and a rocker arm for regulating the turning of the threaded rod, an electromagnet and a timer all powered by a battery. The specification states that rocker arm rotates the threaded rod and that the spring assists the movement of the piston. This implies that the threaded rod is provided with a conventional screw thread requiring an extremely powerful drive for the toothed wheel. Such a device is not particularly practical requiring a substantial force to rotate the threaded shaft and move the piston. Since a substantial force is required to move the piston to expel the lubricant, an escapement rocker and electromagnet operating in the manner shown would need to be extremely strong and would require very large batteries to power them. The cap or chamber containing the control mechanism and batteries is positioned axially behind a helical spring and would need to be many times larger than illustrated in the drawings.
It is also known to provide devices for automatically dispensing medicaments into patients as disclosed, for example, in U.S. Pat. Nos. 4,313,439, 4,300,554, 4,059,110, 4,921,487, WO-A-82/00589 and GB-A-2,166,497. At least some of these medicament dispensing devices use a combination of spring means with electrically controlled escapement means for regulating the dispensing rate of the medicament into patients. All these known medicament dispensing devices are designed to hold and actuate conventional medical syringes by temporarily incorporating them into large housings fitted with powerful geared motors and actuating systems which require large electric batteries to operate them. They are consequently relatively bulky and the ratio of the overall volume of the complete dispensing devices to the volume of medicament the devices are to dispense is typically between 20:1 and 60:1. This relative bulkiness is of no disadvantage in the case of a medicament dispenser because the amount of medicament required to be dispensed is relatively small and the complete device can be suspended on a patients belt or on a hospital bed rail and the medicament can be fed to the patient""s body via a tube fitted to a needle or catheter. These known medicament dispensing devices are typically intended to dispense medicaments over a short time span, e.g. several hours, and are not designed to dispense fluent material for longer periods of time, e.g. over several months.
One aim of the present invention is to provide an improved lubricating device in the form of a self-contained automatic lubricator. Another aim of the invention is to provide a lubricating device in which the dispensing of lubricant can be controlled and which overcomes the disadvantages of known self-contained automatic lubricators and other types of single-point lubricator.
Preferred additional aims are to provide a lubricating device which is self-contained, is of compact design, does not use large battery packs and/or motors for operation over an extended period of time and is spring-operated.
According to the present invention there is provided a lubricating device as claimed in the ensuing claim 1.
With a lubricating device according to the invention the source of power for moving the piston means is provided by the spring means. The electrical means can be operated at relatively low power since its main function is to power the control means for controlling the release of spring energy from the helical spring means as it moves from its compressed condition to its expanded position. Thus low power batteries housed within the lubricating device can be employed.
By arranging for the gearing to be positioned either inside, so as to be surrounded by, the helical spring means, or (radially) outside the helical spring means, the lubricating device can be made of a compact design compared with known designs in which the gearing is positioned axially in-line with spring means.
Preferably the escapement mechanism and/or the electrical means are/is either positioned with the gearing inside, so as to be surrounded by, the helical spring means, or, alternatively, are positioned with the gearing radially outside the centrally positioned helical spring means. In either case the lubricating device is of a compact, self-contained design. Preferably the lubricating device has a ratio of overall volume of the complete lubricating device to the volume of lubricant it is to dispense at no more than 5:1 and preferably no more than 2.5:1. Such a compact, self-contained automatic lubricator is of completely different design to known lubricators and other dispensers of fluent material.
The control means may further comprise a control device providing a mechanical connection between the gearing and the piston means. Suitably the control device is either positioned with the gearing inside, so as to be surrounded by, the helical spring means, or is positioned with the gearing radially outside the centrally positioned helical spring means. Preferably the control device comprises at least one rack member which is connected to the piston means and is in mechanical connection with at least one gear wheel of the gearing. In this case the or each rack member may have at least two sets of teeth in mechanical connection with at least two gear wheels of said gearing.
Alternatively, for example, the control device may comprise a rotatable screw-threaded member screw-threadedly engaged with screw means provided on the piston means and connected to said gearing, movement of the piston from its rear position to its forward position by the spring means causing the screw-threaded member to turn. The turning of the screw-threaded member by the spring force acting through the piston means is controlled by the escapement mechanism and the gearing to regulate the movement of the piston means.
Preferably the spring means comprises one or more helical compression springs which are relatively powerful and provide the motive force required to move the piston means. The compression spring or springs may be disposed slidingly adjacent to the side walls of the cylinder means to exert pressure directly on the piston means in order to expel the lubricant from the discharge outlet, or may be disposed slidingly within a centrally positioned tubular extension of the piston to similarly exert pressure directly on the piston. The compression spring(s) may be selected with characteristics that ensure that when the piston means is moved to the end of its stroke to fully discharge the lubricant, the or each spring utilises only part of its extending capacity so as to ensure that it continues to apply adequate force even at the end of the stroke of the piston means. Two or more compression springs may be provided arranged coaxially within each other. The spring force is transmitted from one end of a compression spring to the other end of a radially adjacent compression spring by means of a xe2x80x9cfloatingxe2x80x9d force transmission member arranged between the compression springs. The provision of two or more such helical compression springs combined with one or more such xe2x80x9cfloatingxe2x80x9d transmission members enables greater pressure to be exerted on the piston within a compact design. In general the provision of more than one helical spring is more suited to the arrangement in which the helical spring means surround the gearing. However it is also possible for the helical spring means to comprise more than one helical spring in the case where the gearing is positioned radially outside the spring means. Suitably
Suitably the electrical means comprises an electric battery, actuation means, such as a servo or solenoid device, for operating the escapement mechanism, and settable timing means for controlling the frequency of operation of the actuation means for controlling the rate of discharge of the fluent lubricant from the variable volume chamber. The electrical means is intended to enable the operation of the escapement mechanism to be adjusted so that the rate of dispensing of lubricant can be preset and/or adjusted as required. The timing means can be connected to a dial in the outer casing of the lubricating device to enable a user to rotate the dial from an inactive or off position to any of a selection of settings to operate the control means to manipulate the escapement mechanism in appropriately timed pulses to discharge the lubricant at the rate selected by the user. Conveniently the timing means is settable for dispensing lubricant over a period of up to 36 months, typically from 1 to 24 months.
It is preferred for lightness and cost of manufacture for the gearing to comprise a plurality of meshing gear wheels made of plastics material.
The escapement mechanism may be similar to those used to control mechanical clockwork movements, e.g. it may comprise a pivoted arm with two hook shaped projections which alternatively engage and disengage with teeth of a toothed wheel of the gearing as the arm is moved from side to side. As one hook shaped projection disengages from one tooth and allows the toothed gear wheel to turn under pressure from the spring means, the other projection engages with another tooth and halts the movement until the escapement arm is moved again. Only light force is required to move or operate such an escapement mechanism and yet the powerful spring force of the spring means can be released in increments. Alternative escapement mechanisms, e.g. an electro magnetically operated braking device, may be provided instead of a conventional mechanical escapement mechanism of the type used to control clockwork movements.
In the preferred design of lubricating device, the motive force for the lubricating device is provided by one or more powerful, yet preferably compact and inexpensive, helical springs and the transmission of the motive force is arranged by means of rack and pinion means combined with simple gearing and an escapement mechanism. The control of the escapement mechanism is effected by means of light duty electrical means powered by a small battery. The resultant lubricating device is a self-contained, automatic self-contained automatic lubricator which is compact, light in weight and inexpensive, and yet it is able to offer an accurate means of dispensing lubricants at precise selected rates irrespective of ambient temperature, the varying characteristic of the spring or springs, and the resistance of bearing lubricant channels.